The invention relates generally to the field of body position indicator devices and more particularly to the field of devices which are worn on the body and which produce a signal in response to the angle of deviation from a set reference angle. For example, in one particular application of the invention, the device is worn on the upper torso of an individual and set to indicate when the individual bends at the waist to too great a degree, thereby causing his torso to exceed a given angle of deviation from true vertical (taken to be the line of gravitational orientation). This application of the invention will be utilized in the description of the invention.
There are situations where it is important that an individual maintain his torso in an upright position, and therefore it would be useful to have a simple, inexpensive device available to be worn on the body which will be non-obtrusive yet alert the wearer whenever his torso deviates a determined amount from true vertical position. The device would best be adjustable such that a given permissible range of movement from vertical can be individually set for each wearer.
For example, it is well known that the correct technique for lifting heavy or bulky items by hand is to bend at the knees to lower the body while maintaining a fairly erect back. In this technique, the lifting is performed by the leg muscles and does not put a strain on the spine or back muscles. This is the preferred lifting technique, since the spinal disks are susceptible to compressive injury and the back muscles are weaker and much more susceptible to injury than the leg muscles. The incorrect technique, though the technique most often used, is to bend at the waist and keep the knees straight. With this technique, the stressed leverage points are inappropriately located at the lower back rather than in the legs, and the potential for injury to the back is high. Each year, thousands of working hours are lost due to injuries directly related to improper lifting techniques, and these lost hours represent many thousands of dollars in lost productivity. The device of the invention can be used to properly train workmen in the correct lifting techniques or can be worn on the job to act as a reminder or warning when improper technique is attempted.
Another example of a setting where the device of the invention is useful is in a post-injury or post-surgery situation. It may be determined by the physician that a limited range of motion is desirable or required due to specific injuries or operations performed on an individual. The device can be set to alert the individual when this allowable range of motion is exceeded.
There are various types of devices currently in existence which relate to this field. In the physical restraint category, there are known restrictive harnesses which consist of motion limiting straps, fabric or formed material. These are worn by an individual and prevent movement beyond the allowable range. This type of device is uncomfortable, bulky, and psychologically frustrating to the wearer. In this same vein, there are known cinch belts which are worn around the waist which physically bind or dig into the skin of the wearer causing such discomfort that the wearer straightens up to the correct vertical position. The negatives of this apparatus are easily apparent.
Devices which are more distantly related are found in the posture training field. These devices often indicate poor posture or slumping rather than vertical displacement. See for example, U.S. Pat. Nos. 4,007,733 to Celeste et al and 3,670,320 to Palmer, both involving elastic tensioning devices. Badorvinac in U.S. Pat. No. 2,494,278 shows a device responsive to both frontward and rearward angular displacement of the head, consisting simply of a roller contained in a slotted housing which is worn on a hat. No adjustment is possible and the device is only suitable for head movement. Likewise, Bechtel in U.S. Pat. No. 4,196,524 teaches a more complicated device for indicating head movement. This device is worn on the top of the head and an alarm goes off if the head is dipped in any direction. None of these devices are capable of being worn on the torso to indicate angular movement out of vertical.
Finally, Leighton in U.S. Pat. No. 2,565,482 shows a device used to measure angular body movements. The device consists of a weighted pointer mounted on a pivot such that the pointer remains vertical as the device in angled. A non-pivoting dial is used to measure the angle of movement. The device only measures degree of movement and cannot be used to warn of impermissible motion.